A microphone, also known as a mic or mike, is an acoustic-to-electric transducer or sensor that converts sound within a medium, typically air, into an electrical signal. Microphones are used in many applications such as telephones, gaming consoles, hearing aids, public address systems, film and video production, live and recorded audio engineering, two-way radios, radio and television broadcasting, and in computers for recording voice, speech recognition, voice-over-IP (VoIP), and for non-acoustic purposes such as ultrasonic checking or knock sensors.
Most microphones today use electromagnetic induction (dynamic microphones), capacitance change (condenser microphones) or piezoelectricity (piezoelectric microphones) to produce an electrical signal from air pressure variations. Microphones also must be used typically in conjunction with a preamplifier before the signal can be amplified with an audio power amplifier for use and/or recording.
Dynamic microphones work via electromagnetic induction and are robust, relatively inexpensive and resistant to moisture. This, coupled with their potentially high gain before feedback, makes them ideal for on-stage use. The most common dynamic microphones today are moving-coil microphones that exploit a small movable induction coil, positioned in the magnetic field of a permanent magnet, which is attached to the diaphragm. When the diaphragm vibrates under an acoustic stimulus then the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction. A single dynamic membrane does not respond linearly to all audio frequencies and accordingly some dynamic microphones exploit multiple membranes for the different parts of the audio spectrum and then combine the resulting signals. Combining the multiple signals correctly is difficult and designs that do this tend to be expensive whilst some other designs are more specifically aimed towards isolated parts of the audio spectrum.
Ribbon microphones exploit a thin, usually corrugated metal ribbon suspended in a magnetic field. The ribbon is electrically connected to the microphone's output, and its vibration within the magnetic field generates the electrical signal. Ribbon microphones are similar to moving coil microphones in the sense that both produce sound by means of magnetic induction. However, basic ribbon microphones detect sound in a bi-directional pattern because the ribbon, which is open to sound both front and back, responds to the pressure gradient rather than the sound pressure.
Ribbon microphones were once delicate, and expensive, but modern materials have made certain present-day ribbon microphones very durable and suitable to applications outside the once limiting studio environment. Ribbon microphones are prized for their ability to capture high-frequency detail, comparing very favorably with condenser microphones, which can often sound subjectively “aggressive” or “brittle” in the high end of the frequency spectrum. Due to their bidirectional pick-up pattern, ribbon microphones are often used in pairs to produce the Blumlein Pair recording array. In addition to the standard bidirectional pick-up pattern, ribbon microphones can also be configured by enclosing different portions of the ribbon in an acoustic trap or baffle, allowing cardioid, hypercardioid, omnidirectional, and variable polar patterns, for example, although these configurations are much less common.
A loudspeaker, also known as a speaker or loud-speaker, produces sound in response to an electrical signal input. The most common speaker used today is the dynamic speaker which operates on the same basic principle as a dynamic microphone, but in reverse, in order to produce sound from an electrical signal. When an alternating current electrical audio signal input is applied through the voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction, which causes a paper cone attached to the coil to move back and forth, pushing on the air to create sound waves.
To adequately reproduce a wide range of frequencies, many loudspeaker systems employ more than one loudspeaker, particularly for higher sound pressure level or maximum accuracy. Individual loudspeaker are used to reproduce different frequency ranges. These loudspeakers are typically referred to as subwoofers (for very low frequencies); woofers (low frequencies); mid-range speakers (middle frequencies); tweeters (high frequencies); and sometimes supertweeters, optimized for the highest audible frequencies.
As with microphones a ribbon speaker employing a thin metal film ribbon suspended in a magnetic field offers a very good high frequency response due to the low mass of the ribbon and as such have tended to be employed in tweeters and supertweeters. An extension of ribbons, although strictly not true ribbon speakers, are planar magnetic speakers employing printed or embedded conductors on a flat diaphragm wherein the current flowing within the coil interacts with the magnetic field, which if appropriately designed yields a membrane moving without bending or wrinkling wherein the large percentage of the membrane surface experiencing the driving force reduces resonance issues in coil-driven flat diaphragms.
With portable multimedia players, portable gaming systems, smartphones, etc. the market for loudspeakers and microphones has expanded significantly over the past decade eclipsing the volumes from residential applications etc. In 2013 the global audiovisual headphone market was estimated at approximately $8 billion with nearly 300 million sets sold. Within this headphones with microphones were an emerging trend accounting for nearly 20% of global shipments and expected to grow to 40% in 2017. At the same time within portable applications low cost headphones such as in-ear “ear buds” have been losing significant market share to the traditional over-the-ear headphones and on-ear headphones primarily as the result of marketing and branding from companies such as Beats™, SkullCandy™. As such premium audiovisual (AV) equipment is now dominating a market where historically AV devices were merely necessary accessories.
Accordingly, it would be beneficial to leverage the technical performance achievable from ribbon microphones which currently reside primarily within recording studios into the broader global marketplace of AV equipment. Similarly it would be beneficial to leverage ribbon and/or planar loudspeaker designs into this broader global marketplace of AV equipment. It would be further beneficial for new materials to be established improving the mechanical strength of ribbon microphones and loudspeaker as well as reducing the material and implementation costs of such microphones and loudspeakers.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.